Integrated multiphoton excitation fluorescence and scanning electron microscopies; allow us to refine the information on the cell surface receptor distribution. In multiphoton microscopy microscopy allows to reduce the out-of-focus fluorescence, thereby facilitating observations of cell surface phenomena as signals from the interior are rejected. In scanning electron microscopy, distribution of markers can be verified at the ultrastructural level. This integrated approach is particularly powerful when combined with cryotechniques. Recent advances in instrumentation call for the development of the probes which will be detectable in both methods of microscopy. A step in this direction was made with successful conjugation to antibodies: a. 3 nm colloidal gold - the smallest gold bead detectable with SEM on the cell surface and b. tetramethyl rhodamine - suitable for two-photon excitation. In this project other attempts of derivatizations will be pursued.